The present invention relates to a monitor for expansion joints such as those utilized in parking garages wherein the concrete decks of the garage may typically have an expansion joint every fifty feet in order to accommodate the expansion and contraction of the concrete under different temperature conditions. The expansion joint opening is sealed for a variety of reasons. For example, it is sealed with a conventional flexible expansion joint to prevent water, salts debris and the like from passing through the opening to the space underneath. Furthermore, it is desirable to provide a an upper surface on the expansion joint which is relatively flush with the upper surfaces of adjacent concrete members so that no safety hazard is presented to persons wearing high heels or using wheelchairs. These expansion joints fail for a number of reasons, one being that they cannot accommodate the movement between the concrete members with which they are used.
Concrete, under controlled conditions, has a definable movement factor. The known coefficient of expansion and contraction of concrete, and the predictable high and low temperature range in the area where the concrete is placed, serve as a guide for engineers in determining the placement of the expansion joints and the size of the joint required to accommodate the predicted total movement due to expansion and contraction. There is a need for a device which will accurately monitor the movement of an expansion joint in order to determine whether or not the calculated and actual movements of the joint are the same. Furthermore, when rehabilitating and reinstalling failed expansion joints, it is important to know exactly how much total movement has occurred so that a new expansion joint can be installed which is designed to accommodate the known total movement.
The minimum opening between adjacent concrete members will, of course, occur on the hottest day of the year, while the maximum opening between adjacent concrete members will occur on the coldest day of the year. A person could go to an installed expansion joint and measure the gap on both the hottest and coldest day of the year to obtain this information, but such a procedure is not practical since it is impossible to predict when the hottest and coldest days of the year will occur. Furthermore, it is not practical to visit all of the existing expansion joints which may need future replacement. It is therefore a principal objective of the invention to provide a device for measuring total movement of an expansion joint which is simple and inexpensive in construction, yet which is durable and will provide very accurate information as to the total movement which has occurred during hot and cold weather throughout a period of a year or more.